Depending on what year Capri the rear end is from (and if it's from a 2.0l), it's a 3.44. The V6 Capris had 3.22. Early 1600 Capris had a 3.89. If the rear end is indeed that high, then it could be from something else. Did you look to see if there is a tag with the ratio on the rear end bolts?

The 4.56 ratio made me think also that it might be something else . Altough there are many more ratio's available for this axle i would not think anything higher as 4.1 would end up in a normal way in USA .
We realy need more info to answer the question .

Put in neutral and jack up one rear wheel. Turn the wheel 2 full turns and count the number of turns the driveshaft makes. That is your ratio._________________Bayless
1948 Prefect E93A
http://sailok.com/enfoprefect

My Cortina has a 3.9:1. Thus two full rotations of the wheel will give almost 4 rotations of the driveshaft. A bit beyond 4 turns; 4:11 a bit more; 4.44 and so on.
It is difficult to accurately determine the ratio by doing it this way. You may have to remove the back plate of the Atlas R/E and count the gear teeth.